Switchfoot614

2008 GTS purchased from a non porsche dealer earlier this year.. 52k miles and super clean. Had the local dealer do a PPI, never checked the DME for over-revs. Recently had a hollow congo drum noise and took it to my local porsche master mechanic. Fixed the broken vent tube which runs from the d/s pcv valve to the front of the d/s cylinder head. Congo gone. She does rattle a bit off idle, power is still what I know to be "good". I finally said that its time to figure this out before I grenade the engine. Teardown nearly complete and the findings are:

Upper timing chain was super loose once the timing cover came off.
Upper chain tensioning bolt (hyd with spring backup) still has spring pressure though there are two nasty machined divots where it has been slapping on the tensioner rail.
d/s cam position sensor reads 3.5 degrees compensation
crank and p/s cams appeared to be in time and the d/s bank appears out.
I have to get the proper adjustment tool en route so I know for sure.
high pressure fuel pump has to come out so lifters can be inspected (might be source of rattle, or it was all the tensioner)
Cylinder 5 ports are dirtier than the rest
cylinder 5 spark plug insulator is gray in color where as the rest are white.

List of replacements planned:
upper chain, tensioner bolt
both cam adjusters and actuators
any suspect lifters in the d/s head (source of all of the rattle)

Has anyone else dived into one of these engines and can offer any advice?

I'll attempt to add photos

Kevin M.

You're obviously a mechanic, safe to say very few of us have cracked open the engine. We'd love to see some pics and learn from you.

Switchfoot614

Ha! I am definitely not a mechanic by trade! However, I have built my share of VW Vr6 engines for street/race applications. The teardown continues tomorrow so I can assess the total damage and get parts ordered. Valve covers/timing covers are headed over to polydyn to be cleaned and coated (likely a gunmetal alaphuric urethane/Ceramic blend). I shall resist the urge to pull the heads and port them.

My guess is that during the over-rev, the timing chain stretched, the tensioner bolt was damaged hydraulically and the chain skipped a tooth. As there isn't truly a way to test the cam tensioners (that i've found in alldata yet), I'm going to replace them both. $420 or so each and $120 or so a piece for the hydraulic solenoids. Damage to the tensioner bolt as shown below is definitely a sign that it was fully extended and the hydraulic performance is gone. The rattle was likely the chain slapping onto the guide and wearing on the tensioner bolt as shown by the divots. I might be wrong but it's tough to tell.

Robert

blackland

I am surprised it doesnt have a limiter to protect from the overspeed?

Switchfoot614

mechanical over-rev.. near redline and down 2+ gears will cause this. Tiptronic's will not allow this scenario to occur.

Switchfoot614

HP fuel pump removed and the camshafts are all out. I'm digging to determine if lifter squish by hand pressure indicates a bad lifter or not. Most do not compress under light pressure, some do. This is going to get $$$$$ quick.

Any lifter knowledge is appreciated.

Slow Guy

Might check w/ Steve Weiner (Rennsport Systems), not sure if they do anything with Cayenne's but it doesn't hurt to ask. He's a big help on the 993 forum and knows a great deal about the 993 lifters.

deilenberger

Also - be a good thing if before you posted pics here - if you resized them to something reasonable. Your photo is about 4 screens wide. Use a free tool like "Irfanview" and make them no wider than 1024 pixels in the horizontal direction. 800 pixels is still more than adequate.